Ensure the PTT state is set to on when sending USRP; Add a timeout to send a end of transmission to USRP when DVM is done transmitting

dvmusrp/Network.DVM.cs

@@ -22,6 +22,9 @@ namespace dvmusrp
     public class NetworkDVM : Network
     {
         private NetworkUSRP usrpNetwork;
+        private DateTime lastPacketReceivedTime;
+        private TimeSpan callTimeout = TimeSpan.FromSeconds(1);
+        private bool eotSent = false;
 
         /// <summary>
         /// Creates an instance of <see cref="NetworkDVM"/>
@@ -30,7 +33,10 @@ namespace dvmusrp
         /// <param name="sendPort"></param>
         /// <param name="receiveAddress"></param>
         /// <param name="sendAddress"></param>
-        public NetworkDVM(int receivePort, int sendPort, string receiveAddress, string sendAddress) : base(receivePort, sendPort, receiveAddress, sendAddress) { }
+        public NetworkDVM(int receivePort, int sendPort, string receiveAddress, string sendAddress) : base(receivePort, sendPort, receiveAddress, sendAddress)
+        {
+            lastPacketReceivedTime = DateTime.Now;
+        }
 
         /// <summary>
         /// Helper to set the instance of <see cref="NetworkUSRP"/>
@@ -54,9 +60,26 @@ namespace dvmusrp
                     {
                         try
                         {
-                            var receivedResult = await udpClient.ReceiveAsync();
+                            Task<UdpReceiveResult> receivedTask = udpClient.ReceiveAsync();
+                            Task timeoutTask = Task.Delay(callTimeout);
+
+                            Task completedTask = await Task.WhenAny(receivedTask, timeoutTask);
+
+                            if (completedTask == timeoutTask)
+                            {
+                                if (!eotSent)
+                                {
+                                    SendUsrpEOT();
+                                    eotSent = true;
+                                }
+                                continue;
+                            }
+
+                            eotSent = false;
+
+                            lastPacketReceivedTime = DateTime.Now;
 
-                            ForwardToUSRP(receivedResult.Buffer);
+                            ForwardToUSRP(receivedTask.Result.Buffer);
                         }
                         catch (Exception ex)
                         {
@@ -91,6 +114,8 @@ namespace dvmusrp
                 Array.Copy(packet, 4, audio, 0, audio.Length); // No meta data, just skip PCM length
             }
 
+            usrpHeader[15] = 1; // Set PTT state to on
+
             Array.Copy(Encoding.ASCII.GetBytes("USRP"), usrpHeader, 4);
             Array.Copy(usrpHeader, usrpData, usrpHeader.Length);
             Array.Copy(audio, 0, usrpData, 32, audio.Length);
@@ -100,6 +125,17 @@ namespace dvmusrp
             usrpNetwork.SendData(usrpData);
         }
 
+        /// <summary>
+        /// Helper to send a EOT to USRP
+        /// </summary>
+        public void SendUsrpEOT()
+        {
+            byte[] usrpHeader = new byte[32];
+            Array.Copy(Encoding.ASCII.GetBytes("USRP"), usrpHeader, 4);
+
+            usrpNetwork.SendData(usrpHeader);
+        }
+
         /// <summary>
         /// Helper to send data to DVM
         /// </summary>